SwapChain is a special render buffer, which is used as a final rendering target to output to display. Each time a frame has been completed in Buffer1, it becomes Buffer2 to be displayed on the output. The previous Buffer2 becomes Buffer1 to create the next frame. This constant change between back and front buffer is called swapping or flipping.

SwapChain generation
You can find the SwapChain Class in DXGI. The buffer generation is simple: